Preparation of keto acid compounds



under the conditions of the reaction.

Patented Mar. 18 1952 2,589,314 PREPARATION OF KETO ACID COMPOUNDS Lyle 0. Woods and Howard M. Teeter, Peoria, 111., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application June 27, 1950, Serial No. 170,676

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

This application is made under the act of March 3, 1883, as amended by the act of April 30,

1 928, and the invention herein described, it patented in any country m ay be manufactured "and used by or for the Government of the United 'States of America for governmental purposes throughout the world without the payment to us fatty esters and the corresponding free acids.

According to our invention fatty acid esters which contain 8 or more carbon atoms in the acid chain and which also contain the chlorohydrin ,ether grouping:

in the chain are converted into corresponding keto derivatives by a reaction which apparently proceeds as follows:

t t A -i -o-h RCl In the above formulae, R. represents an aliphatic or aromatic group, as for example, methyl, propyl, phenyl, and the like, attached to the ether oxygen through a non-tertiary, i. e., a primary or secondary carbon atom. The ester group of the-compound does not enter into the conversion and should be a radical having a normally stable structure, as well as being devoid of substituents which would undergo chemical alteration under the conditions of our process. It" may be any organic radical normally stable It may be,

for example, alkyl, aryl, cycloalkyl, aralkyl, and

sired keto derivative is produced in good yield by a relatively simple process. g 1

The keto derivatives of long chain fatty esters and the corresponding free acids are useful intermediates in chemical syntheses and find use Hitherto these acid compounds have been prepared only by elaborate chemical synthesis or by oxidation reactions of fatty acids, such as hydrogenated ricinoleic acid. These prior methods give poor yields and are costly.

The conversion,-according to our invention, is brought about by subjecting the fatty acid ester containing the 'chlorohydrin ether group to the action of heat at a temperature within the range of 150-300 C. and a pressure of l to 200 mini-'- meters of mercury.- The reaction is usually complete at the end of two to four hours. Within these rather narrow limits we have discovered that the desired compounds are produced in good yield. Excellent yields are obtained in the case of the methoxychloro derivative of methyl oleate within the optimum range of 270-290 C. tem perature and to 150 millimeters pressure. The reaction is usually complete after 2 hours, but the heating may be continued for a longer period to insure maximum yields. In. the case of alkyl esters of methoxychloro stearic acid, these opti-''- mum ranges are particularly applicable.

The product of the conversion is the keto acid ester. It may be isolated from the reaction mix,- ture by any convenient means such as distillation or fractional crystallization. The correspondin free acid is obtained simply by saponification of the ester by conventional procedures. As stated previously, the ester group of the starting mate.- riaLwhich is split off by saponification is not affected by the conditions of our conversion process. Y

The starting compounds for our process may be prepared by chlorination with elementary chlorine of the'appropriate fatty acid .or. its ester in the presence of an aliphatic or aromatic alco: hol. A method wehave found to give excellent results for preparing these starting compounds is by the reaction of the alcohol, and molecular equivalents of the fatty. acid ester and t-butyl hypochlorite. This method produces a minimum of byproducts, and a specific embodiment of it 1 will be described in the examples which'follow.

in the manufacture of plastics, lubricants, waxes,

detergents, corrosion inhibitors and the like.

It possesses the additional advantage that the crude product, after removal of excess alcohol, may be used directly for our conversion.

Erdmple 1 with stirring during a period of minutes. The temperature of the. reaction was kept below C. The reaction mixture was allowed to stand 3 for one hour after which excess methanol was removed by distillation. The residue, methyl methoxychloro stearate, was heated with stirring for four hours at 280 C. and a pressure of 100 mm. of mercury. After cooling, the reaction mixture comprised a semisolid mass and contained 3.26 percent of carbonyl groups by hydroxylamine titration. This corresponds to a yield of 64 percent of methyl ketostearate. This titration method is described in J. Am. Oil Chemists Soc.

26, 366, July 1949. The product purified either by distillation or fractional crystallization had a melting point of 4243 C. S-aponification by alcoholic KOH yielded ketostearic acid, having a melting point of 71-'72 C.

Analyses:

Methyl ketostearat-e, Calc'd: OCH3, 10.39; sap. eq. 312.5. Found: OCHs, 10.36; sap. eq. 309.7. Ketostearic acid, Calcd.:- C, 72.37; H, 11.47; Neut. eq. 298.4. Found: C. 72.05; H, 11.42; Neut. eq. 300.5.

Example 2 In a manner similar to that described in Example l, n-propyl oleate was converted to the methoxychloro derivative, heated at 275-285 C. and approximately 100 mm. of mercury. The product, methyl ketostearate, had a melting point of 42-43 C.

' Example 3 By a procedure similar to Examples 1 and 2 isooctyl ketostearate was prepared from isooctyl oleate. It had a melting point of 35-36 C.

Analyses:

' Calcd.: C, 76.04; H, 12.27. Found: C, 76.15;

Example 4 Methyllcetostearate from methyl butoasychloro steamte.Methyl butoxychloro'stearate was prepared by the reaction of methyl oleate and t-butyl hypochlorite in the presence of a 40-mole excess of n-butanol. excess n-butanol were removed by distillation first at atmospheric pressure and then in vacuo.

The temperature during distillation did not exceed 150 C.; however, the residue of crude methyl butoxychloro stearate was found by analysis to contain 7.8 percent of methyl ketostearate, indicating that some conversion had occurred during the distillation. This residue was further heated for 4 hours at 284 C. and a pressure of 100 mm. of mercury. On cooling, crystals of methyl ketostearate separate. Analysis of the product showed the presence of 3.73 percent of carbonyl, corresponding to a yield of about 73 percent of methyl ketostearate. It was purified as in Example 1.

We claim:

1. Method which comprises subjecting a fatty acid ester containing at least 8 carbon atoms in the carbon chain of the acid radical, said chain also containing the chlorohydrin ether grouping:

can R 1 :1

in which R represents a-radical of the group consisting of aliphatic and aromatic radicals attached to the ether oxygen through a non-ter- Byproduct t-butancl and tiary carbon atom to the action of heat at a temperature within the range of 150-300 C. and a pressure of 1 to 200 millimeters of mercury to convert the chlorohydrin ether grouping into the ii I group, and isolating the resulting keto acid ester from the reaction mixture.

2. The method of claim 1 in which the reaction is carried out within the range of 270-290 C. temperature and to 150 millimeters pressure for two to four hours.

3. Method which comprises subjecting a fatty acid ester containing at least 8 carbon atoms in the carbon chain of the acid radical, said chain also containing the chlorohydrin ether grouping:

in which R, represents a radical of the group consisting of aliphatic and aromatic radicals to the action of heat at a temperature within the range of 150-300' C. and a pressure of l to 200 millimeters of mercury to convert the chlorohydrin ether grouping into the group, and isolating the resulting keto acid ester from the reaction mixture, and saponifying said keto acid ester to the corresponding free keto acid.

4. The method which comprises heating an alkyl ester of methoxychloro stearic acid to a temperature of 270-290 C. and a pressure of 50 to 150 millimeters of mercury for a period of two to four hours and isolating the resulting methyl alkyl ester of ketostearic acid from the reaction mixture.

5. The method which comprises heating an alkyl ester of methoxychloro stearic acid to a temperature of 270-290 C. and a pressure of 50 to 150 millimeters of mercury for a period of two to four hours and isolating the resulting methyl alkyl ester of ketostearic acid from the reaction mixture and saponifying said alkyl ester of ketostearic acid to ketostearic acid.

6. The method which comprises reacting methyl oleate with approximately a molecular equivalent of t-butyl hypochlorite in the presence of methanol at a temperature below 60 C. to

" produce methyl methoxychloro stearate, removing excess methanol from the reaction mixture, heating the residue at a temperature of 270- 290 C. and a pressure of approximately millimeters of mercury for a period of two to four hours and isolating the resulting methyl ketostearate from the reaction mixture.

LYLE C. WOODS.

HOWARD M. TEETER.

REFERENCES CITED The following references are of record in the file of this patent:

Nicholet a a1. Jr., Am. Chem. Soc. 52 (1936),.

pages 1186-1191. 

1. METHOD WHICH COMPRISES SUBJECTING A FATTY ACID ESTER CONTAINING AT LEAST 8 CARBON ATOMS IN THE CARBON CHAIN OF THE ACID RADICAL, SAID CHAIN ALSO CONTAINING THE CHLOROHYDRIN ETHER GROUPING: 